The invention relates to a work machine equipped with a boom, such as, for instance, mobile concrete pumps, pump mixers, excavators or cranes generally have at least two boom arms, which are mutually pivotable in order to be able to fold up the boom, which can have a considerable length, in a space-saving manner for transport. The boom arms are here placed in the folded state one upon another, wherein only the last boom arm, which has a free end, is supported with its free end, or close to the free end, on a chassis-fixed supporting device. By contrast, the further boom arms resting one upon another are respectively supported on the next lower boom arm. For this purpose, supporting devices, on which the respectively next upper boom arm of the folded boom is supported, are often arranged on the boom arms. In many smaller machines, for instance in pump mixers, which generally have a substantially smaller boom than a truck-mounted concrete pump and on the chassis of which, due to further devices like the mixing drum, there is little space available, such a support is often not possible, however.